This supplemental grant application is submitted for 2 reasons: 1) to request funds for equipment disallowed to be transferred to present institution, and 2) to expand the present grant by 2 projects. The specific aims of the projects are: 1) to determine if exercise at 50% of maximum oxygen consumption can stimulate coronary collateral growth in dogs with a chronic, fixed, subtotal occlusion (a previous study from this laboratory has shown that exercise almost doubled collateral formation following gradual, but total, circumflex occlusion), and 2) to study if hypertension, secondary to coarctation of the aorta, stimulates coronary collateral formation (to test the hypothesis that pressure induces collateral growth) and to determine quantitatively if coronary flow-to-mass ratio changes with ensuing myocardial hypertrophy in short and long-term hypertension. Structural changes of the coronary vasculature will be determined in an isolated heart perfusion system during maximal vasodilation with adenosine (in accordance with previously established procedures). The long-term objectives of these investigations are to quantitate the coronary vascular adaptations to pathological conditions and to obtain insight into the mechanisms governing coronary collateral growth. Coronary occlusion and hypertension are the major contributors to cardiovascular fatalities. An understanding of nature's compensatory responses will help guide clinical treatment of patients.